Marijuana laws continue to relax across the country. We clearly saw in the November initiatives, the spread of medical and recreational marijuana, with 9 states now allowing full legal recreational possession. Impaired Driving enforcement will undoubtedly rise to this occasion, and prosecute more cases of DWI that are alleged on Marijuana impairment. Cannabis (marijuana) affects the body in very different ways than alcohol, and accordingly the burden on the state to prove impairment must be approached differently, and the challenge to the state's case must be particular to the poor understanding of cannabis effects.

Marijuana prohibition has been supported at the Federal level as schedule 1, along side drugs such as heroin, and ranked higher than schedule 2 methamphetamine, one of the most preposterous features of the plant's prohibition. The poor understanding of Marijuana impairment, and how to investigate it, can be attributed to the plant's difficultly to study because of its class 1 scheduling.

The primary impairing ingredient in marijuana, THC, has behavioral effects that are so unique and unpredictable that it can't be classified as a stimulant, sedative, tranquilizer, hallucinogen, etc. The impairing effects of THC are in a class of their own as it were. However, there are effects that are generally considered standard from a physiological standpoint, such as dry mouth, fast breathing, increased pulse and blood pressure, red eyes and dilated pupils, apparent dizziness, and decreased sensitivity to light. These are all observable indications that investigating officers can look for, while they build evidence to charge a DWI based on marijuana impairment.

A strong marijuana DWI case for the state will typically include blood based evidence of THC impairment. The challenge that is difficult to overcome here, is showing whether the consumption is from recent use or previous use, and what those levels mean. Chronic marijuana users will have higher levels of THC metabolites from days prior consumption than what a non-frequent user will have from the same day's consumption. The chronic user's metabolites can show potentially impairing levels after any impairing effects would have surely worn off. Further, it is difficult to create a nexus between THC blood concentrations and the alleged impaired behavior. Patterns of use are key to the conclusions drawn from THC metabolite levels in blood. Also, it is important to note whether blood results are from plasma or whole blood. Plasma results can show double the concentration of THC from whole blood in the same draw.

Standardized field sobriety testing was developed for alcohol impairment investigation, and tends to be insensitive to the differences in other drug related impairment. Because NC is one of the states that insists on resisting the wave of the future, it currently has no regulation, or "per se" level of THC impairment such as Colorado or other legal states, so the challenge for the state's case is in the observations of law enforcement, and questionable blood test results. This makes the challenge of proving Marijuana impairment in NC ripe for legal argument on both sides.